Soft-NUMA Doesn’t Limit MAXDOP

I mentioned that I was planning to set up a soft-NUMA node for each vcpu on a 16 vcpu VM, to evenly distribute incoming connections and thus DOP 1 queries over vcpus. Thomas Kejser et al used this strategy to good effect in “The Data Loading Performance Guide”, which used SQL Server 2008 as a base.https://technet.microsoft.com/en-us/library/dd425070(v=sql.100).aspx

My conversation partner cautioned me that leaving this soft-NUMA configuration in place after the specialized workload would result in DOP 1 queries whether I wanted them or not. The claim was, effectively, a parallel query plan generated by a connection within a soft-NUMA node would have its MAXDOP restricted by the scheduler count (if lower than other MAXDOP contributing factors). Though I wasn’t able to test at the time, I was skeptical: I’d always thought that soft-NUMA was consequential to connection placement, but not to MAXDOP nor to where parallel query workers would be assigned.

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